Environmentally-friendly technique of vehicles is a core technique on which future of vehicle industry depends. Vehicle makers devote their total energy to develop environmentally-friendly vehicles in order to meet environmental and fuel consumption regulations.
Therefore, each vehicle maker has developed electric vehicles (EVs), hybrid electric vehicles (HEVs), fuel cell electric vehicles (FCEVs) as future vehicles.
Since future vehicles have technical limitations such as weight and cost, vehicle makers pay attention to hybrid electric vehicles as alternatives to meet emission regulations and improve fuel consumption performance and fiercely compete to put hybrid electric vehicles to practical use.
A hybrid vehicle uses two or more power sources, and two or more power sources can be combined in various ways. A gasoline engine or a diesel engine using a conventional fossil fuel and a motor/generator driven by electrical energy can be used as the energy sources.
The hybrid electric vehicle uses the motor/generator having relatively better low-speed torque characteristics as a main power source at a low-speed and uses an engine having relatively better high-speed torque characteristics as a main power source at a high-speed.
Since the hybrid electric vehicle stops operation of the engine using the fossil fuel and uses the motor/generator at a low-speed region, fuel consumption may be improved and exhaust gas may be reduced.
An integrated starter and generator (ISG) functions as a motor and a generator. That is, the ISG functions as a motor to rotate a crankshaft when starting an engine, and converts torque of the engine into electrical energy and charges a battery while the engine operates. The ISG can be applied in all the vehicles provided with the engine as well as hybrid electric vehicles.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.